Five members of a banned militant group have been arrested and a homemade bomb was defused in the southern Russian town of Nalchik, a National Anti-terror Committee (NAC) spokesman said on Saturday.

Nalchik, about 300 kilometres from Winter Olympics host city Sochi, is in the foothills of the Caucasus, where Russia faces an insurgency by Islamist militants who have threatened to try to prevent the Games going ahead.

"Security forces have detained five members of a banned international terrorist organization," NAC said in a statement quoted by Russian newswires. An NAC spokesman confirmed with Reuters that the statement was correct.